I suppose it's no wierder than the "Kingdom of the Two Sicilies" even though there's only one Sicily :huh:
Plus; after checking Wikipedia, the Polish name of "Rzeczpospolita Obojga Narodów" literally means "Republic of Two Nations".
Well, actually there were two Sicilies indeed: all of southern Italy, in modern era, was known as "Sicily": Italy and Sicily weren't considered as one "geographical construct". The kingdom of Sicily/Trinacria was officially called "Regno di Sicilia ulteriore", ulteriore (farther) as it was after the lighthouse of Reggio Calabria. Naples was, officially, "Regno di Sicilia citeriore", citeriore (hither) as it was the part of sicily which preceded the lighthouse. After the reunification of the crowns, Ferdinando IV of Naples decided to name it "two sicilies" as for centuries the two realms were divided.
I leave you with a popular doggerel from sicily:
fosti quarto e insieme terzo,
Ferdinando or sei primiero:
e se seguita lo scherzo
finirai per esser zero.
You were fourth and third together,
Ferdinand you are now the first:
and if the joke continues
you're going to be zero.